The invention relates to a method for manufacturing a semiconductor device using an island pattern.
The trend of ultra large-scale integration of semiconductor devices greatly influences the development of minute pattern forming technology. Particularly, the formation process of a photoresist pattern is very important in the formation process of semiconductor devices. Moreover, as the integration density of semiconductor devices has increased, processes for forming island patterns or pillar pattern and associated lithography technology have become very important.
Island patterns and pillar patterns are columnar type patterns or bar type patterns which are independently formed. In forming a photoresist pattern for forming island or pillar patterns, collapse of the photoresist pattern may occur.
The collapse of the photoresist pattern is usually manifested with one of two kinds of phenomena. Firstly, collapse of the pattern may be in the form of peeling, wherein the photoresist pattern falls off from the semiconductor substrate since the adhesion between the photoresist pattern and the semiconductor substrate is weak. Secondly, the photoresist pattern itself may be not be physically solid, so that the pattern is bent or broken.
The incidence of collapse of the photoresist pattern increases as the integration density of semiconductor devices increases since, because the aspect ratio of the photoresist pattern increases, and the thickness of the photoresist should be maintained or increased, the CD (critical dimension) of the photoresist pattern is reduced as the integration density increases.
In addition, in the wet development process, firstly the photoresist is treated by using a developing solution and washed with deionized water, and a spin dry method that rotates a wafer at high speed is performed. Collapse of the photoresist pattern occurs at the moment when the drying process begins.
At this time, collapse of the photoresist pattern occurs because of gravitational force acting on the central part of the gap between the patterns at the moment when deionized water (which was filled between patterns) abruptly evaporates while the spin dry process begins. As a result, weaker patterns collapse among the photoresist patterns.
The dry development process is advantageous in avoiding collapse of the photoresist pattern, in comparison with the wet development process. That is because the collapse of the photoresist pattern does not occur even in case of an aspect ratio with which the collapse of the photoresist pattern can occur in the dry development process.
However, as the aspect ratio is increased, collapse of the photoresist pattern can occur, since the limit of the process margin is reached, even in the dry development process.
Moreover, in the dry development process, the photoresist pattern may become bent or curved, even under conditions where the photoresist pattern does not fall out.
That is, the photoresist pattern is bent since atmospheric moisture coheres to the surface of the photoresist pattern when a wafer is exposed to the atmosphere after the dry development process is performed.
As described above, when the pillar pattern or the island pattern is formed, as the integration density of semiconductor devices is highly increased, the process margin for forming a photoresist pattern is more and more reduced. As a result, problems of decreased yield and lowered reliability due to the fault generation become very serious.